-83.69% is the change from 521 to 85
Calculation steps:
[( 85 - 521 ) ÷ 521] x 100 = -83.69%
Formula
Percentage change = [(85 - 521) / 521] x 100
Subtract the new number by the original number
85 - 521 = -436
-436 ÷ 521 = -0.836852207293666
-0.836852207293666 x 100 = -83.69%